Wireless MAC layer throughput improvements

ABSTRACT

Methods, apparatuses, and systems are presented for transmitting data packets in a wireless network over a multi-access channel involving sequentially sending a plurality of medium access control (MAC) data packets from a transmitter over the multi-access channel, using a physical layer protocol based on a standard physical layer protocol having a short interframe spacing (SIFS), wherein the plurality of MAC data packets includes at least a first data packet and a second data packet separated by a reduced interframe spacing that is less than SIFS, attempting to receive the plurality of MAC data packets at a receiver using the physical layer protocol, including the first data packet and the second data packet separated by the reduced interframe spacing, and sending from the receiver a single acknowledgement packet associated with attempting to receive the plurality of MAC data packets.

BACKGROUND OF THE INVENTION

As wireless networks become increasingly popular, there is an evergreater need to provide higher data throughput from existing bandwidthallocations. Typically, a wireless network must operate within anassigned band of frequencies. This is usually the case regardless of thetype of physical transmission technique utilized. For example, frequencyhopping systems usually must only hop to frequencies contained within afixed range of frequencies. Similarly, spread spectrum systems mustremain within the bounds of a well-defined, frequency band. Of course,frequency division multiplexing system, as well, are confined to fixedbandwidths. Thus, a fundamental performance goal in the implementationof wireless networks is to provide as much data throughput as possiblegiven a particular bandwidth allocation. However, a wireless networktypically has to utilize some sort of protocol to deal with problemsassociated with operating within a multi-access channel environment, inwhich more than one transmitter may transmit in the same channel at aparticular time. For example, the well-known “hidden station” problem isassociated with the fact that not all nodes in a wireless network arewithin radio range of one another. Thus, a node wishing to transmit toanother node may not be able to detect that the a selected channel isoccupied in the vicinity of the other node, such that a packettransmitted to the other node on the selected channel is unlikely to bereceived successfully by the other node. Another problem may simply bethat noise in the channel causes sufficient bit errors for a particulartransmission such that the other node cannot properly receive thetransmission. Thus, it is usually not possible for the transmitter toknow for certain the success of the communication by simply “listening”to the selected channel for its own transmission. The fact that thetransmitter may be able to successfully receive its own transmission isno guarantee that the intended receiver will be able to do the same.

FIG. 1 depicts an illustrative wireless network 100. The wirelessnetwork 100 includes an access point (AP) 102 and stations (STAs) 104and 106. Typically, wireless networks may include numerous APs and STAs,but the simplified wireless network 100 is shown in here forillustrative purposes. Each of the three nodes, AP 102, STA 104, and STA106, must be able to both transmit and receive packets over the wirelessmedium. Different types of communication may be possible. For example,in one arrangement, all communication may be required to go through AP102. Thus, if STA 104 wishes to transmit a packet to STA 106, thetransmission must first be sent to AP 102, then relayed to STA 106. Inanother arrangement, STA 104 may communicate directly with STA 106,without involving AP 102. Regardless of the type of communicationchosen, a fundamental component is a transmission that involves one node(AP or STA) acting as the transmitter and another node (AP or STA)acting as the receiver of the transmission. As mentioned, the wirelessenvironment is such that the transmitter usually cannot tell, by“listening” for its own transmission, whether the transmission it sendshas been properly received by the intended receiver. To deal these andother effects, a multi-access protocol for a wireless network typicallymust provide techniques that handle situations where transmissions arenot properly received. One such technique that has been widely adoptedis the use of an acknowledgement packet.

FIG. 2 illustrates a known approach for sending a number of data packetsfrom a transmitter A, each followed by an acknowledgement packet from areceiver B. As shown in the figure, data packet 202 is sent fromtransmitter A, intended for receiver B. If receiver B properly receivesdata packet 202, it sends an acknowledgement packet 204 back totransmitter A to acknowledge proper receipt of data packet 202. In thismanner, transmitter A is provided with feedback on the success of itstransmission and can react accordingly. For example, each receiver thatdoes properly receive a data packet may be required to send anacknowledgement to the sender within a specified amount of time. Thus,transmitter A may be able measure the time elapsed since it sent datapacket 202. If transmitter A does not receive an acknowledge packet fromreceiver B within the specified amount of time receiver B is required toprovide such acknowledgement, taking into account propagation andprocessing delays, transmitter A may be able to conclude that thetransmission failed and react appropriately, such as initiatere-transmission of the data packet. As shown in FIG. 2, transmitter Amay send another data packet 206 to receiver B, which may then respondwith an acknowledgement packet 208. Similarly, transmitter A may send adata packet 210, to which receiver B may respond with an acknowledgementpacket 212. Thus, this approach involves the receiver sending anacknowledgement packet for each data packet it receives from thetransmitter.

FIG. 3 illustrates a known approach for sending a burst of data packetsfrom a transmitter A, followed by one acknowledgement packet from areceiver B for providing acknowledgement information with regard to allof the data packets in the burst. As shown, transmitter A sends datapackets 302 and 304 and an acknowledgement request packet 306. FIG. 3shows that data packets in the burst are separated by a Short InterframeSpacing (SIFS) defined for the standard physical layer wireless protocolused by transmitter A and receiver B. Within a particular standardphysical layer protocol, SIFS may specify the separation needed betweena data packet and an acknowledgement packet, as well as the separationneeded between consecutive packets sent from a transmitter. Differentstandard physical layer protocols may define different values for SIFS.For example, if transmitter A and receiver B utilize an 802.11a physicallayer protocol, transmitter A and receiver B may be capable of sendingand receiving packets separated by a SIFS defined to be 16 μsec. Asanother example, if transmitter A and receiver B utilize an 802.11bphysical layer protocol, transmitter A and receiver B may be capable oftransmitting and receiving packets separated by a SIFS defined to be 10μsec.

Referring back to FIG. 3, receiver B responds to the acknowledgementrequest packet 306 by sending an acknowledgement packet 308, whichprovides acknowledgement for both data packets 302 and 304, as towhether each packet has been successfully received. Acknowledgementpacket 308 is often referred to as “burst ack” or “group ack” because itprovides acknowledgement information for more than one data packet.Generally, acknowledgement packet 308 provides a bit map that utilizes abit to represent acknowledgement information for each data packet in theburst. Thus, transmitter A may send a burst of many data packets. Inresponse, receiver B would send an acknowledgement that includes a bitmap, with each bit indicating either successful or unsuccessfulreception of a corresponding data packet in the burst.

While the use of “burst ack” has resulted in improvements to datathroughput by reducing the number of acknowledgement packets that mustbe sent for a burst of data packets, such improvements have approached afundamental limit. That is, further improvements to data throughput havebecome exceedingly difficult to achieve given that necessary protocolfunctions must still be carried out, and data throughput performance ofwireless networks for any given allotment of bandwidth appears to have“plateaued.” Yet demand for greater data throughput continues toincrease as available bandwidth remains limited. Thus, there is atremendous need for breaking what seems to be an upper bound for datathroughput in wireless networks to achieve even better data throughputperformance.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to methods, apparatuses, and systems fortransmitting data packets in a wireless network over a multi-accesschannel involving sequentially sending a plurality of medium accesscontrol (MAC) data packets from a transmitter over the multi-accesschannel, using a physical layer protocol based on a standard physicallayer protocol having a short interframe spacing (SIFS), wherein theplurality of MAC data packets includes at least a first data packet anda second data packet separated by a reduced interframe spacing that isless than SIFS, attempting to receive the plurality of MAC data packetsat a receiver using the physical layer protocol, including the firstdata packet and the second data packet separated by the reducedinterframe spacing, and sending from the receiver a singleacknowledgement packet associated with attempting to receive theplurality of MAC data packets.

In one embodiment of the invention, the single acknowledgement packetcontains packet receipt status information to identify a firstsuccessfully received packet and a last successfully received packetfrom the plurality of MAC data packets, wherein the first successfullyreceived packet and the last successfully received packet may beseparately identified by distinct sequence numbers provided in thesingle acknowledgement packet. The reduced interframe spacing may beadjustable within a range between zero and SIFS. The reduced interframespacing may also be automatically adjustable depending on identity ofthe receiver. Further, the wireless network may utilize an 802.11-basedphysical layer protocol.

In another embodiment of the invention, at least a first and a secondmode of operation may be possible, wherein the first mode of operationinvolves the mentioned steps for sequentially sending the plurality ofMAC data packets, attempting to receive the plurality of MAC datapackets, and sending the single acknowledgement packet, and wherein thesecond mode of operation involves, from the transmitter, sequentiallysending a second plurality of MAC data packets over the multi-accesschannel, wherein the second plurality of MAC data packets includes atleast a first data packet and a second data packet separated by areduced interframe spacing that is less than SIFS, at the receiver,attempting to receive the second plurality of MAC data packets,including the first data packet and the second data packet separated bythe second reduced interframe spacing, without sending from the receiveran acknowledgement packet associated with the attempt to receive thesecond plurality of data packets.

In yet another embodiment of the invention, a third mode of operationmay be possible involving, from the transmitter, sequentially sending athird plurality of MAC data packets over the multi-access channel,wherein the third plurality of MAC data packets includes at least afirst data packet and a second data packet separated by SIFS, at thereceiver, attempting to receive the third plurality of MAC data packets,including the first data packet and the second data packet separated bySIFS, and sending from the receiver a single acknowledgement packetassociated with the attempt to receive the third plurality of MAC datapackets.

In addition, the reduced interframe spacing may be dynamicallyadjustable based on which mode of operation is selected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an illustrative wireless network;

FIG. 2 illustrates a known approach for sending a burst of data packetsfrom a transmitter A, each followed by an acknowledgement packet from areceiver B;

FIG. 3 illustrates a known approach for sending a burst of data packetsfrom a transmitter A, followed by one acknowledgement packet from areceiver B for providing acknowledgement information with regard to alldata packets in the burst;

FIG. 4 illustrates an approach for sending a burst of data packetsseparated by a reduced interframe spacing from a transmitter A, followedby a single acknowledgement packet from a receiver B for providingacknowledgement information with regard to the attempt to receive datapackets in the burst, in accordance with one embodiment of the presentinvention;

FIG. 5 is a diagram showing the transmission of the data packets and theacknowledgement request packet from transmitter A to receiver B and thetransmission of the acknowledgement packet from receiver B totransmitter A, as discussed with respect to FIG. 4;

FIG. 6 demonstrates three different scenarios for receiving the datapackets and acknowledgement request packet shown in FIG. 4 andgenerating appropriate acknowledgement packet information, in accordancewith one embodiment of the present invention;

FIG. 7 is a flowchart outlining illustrative steps performed at areceiver for processing received data packets and processing receivedacknowledgement request packets, in accordance with one embodiment ofthe present invention;

FIG. 8 illustrates a queueing structure and the various queue states aspackets are transmitted in a burst ack mode according to one embodimentof the invention.

FIG. 9 is a flowchart outlining illustrative steps performed at atransmitter associated with sending an acknowledgement request packetfollowing a burst of data packets, in accordance with one embodiment ofthe invention;

FIG. 10 illustrates an approach for sending a burst of data packetsseparated by a reduced interframe spacing from a transmitter A, withoutany acknowledgement packet from a receiver B that receives the burst ofdata packets; and

FIG. 11 illustrates an approach for sending a burst of data packetsseparated by a reduced interframe spacing that has been adjusted to zerofrom a transmitter A, followed by a single acknowledgement packet from areceiver B for providing acknowledgement information with regard to theattempt to receive data packets in the burst, in accordance with oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 4 illustrates an approach for sending a burst of data packetsseparated by a reduced interframe spacing from a transmitter A, followedby a single acknowledgement packet from a receiver B for providingacknowledgement information with regard to the attempt to receive datapackets in the burst, in accordance with one embodiment of the presentinvention. Transmitter A operates in accordance with a physical layerprotocol that is based on a standard physical layer wireless protocolhaving a defined SIFS. For example, transmitter A may operate accordingto a physical layer protocol that is based on the standard 802.11aphysical layer wireless protocol, which may have a defined SIFS of 16μsec. The physical layer protocol used may be quite similar to thestandard physical layer protocol on which it is based. However, thephysical layer protocol allows for transmission and receipt of datapackets separated by a reduced interframe spacing that is less than theSIFS defined for the standard physical layer protocol. The physicallayer protocol may be based on different standard physical layerwireless protocols, including various 802.11-based physical layerprotocols such as 802.11 infrared, 802.11 frequency hopping spreadspectrum (FHSS), 802.11a orthogonal frequency division multiplexing(OFDM), 802.11b high rate direct sequence spread spectrum (HR-DSSS),802.11g OFDM, and others. Referring back to FIG. 4, transmitter Asequentially sends data packets 402, 404, 406, and 408, with consecutivedata packets separated by a reduced interframe spacing that is less thanthe SIFS defined for the standard physical layer wireless protocol. Atthe end of the burst of data packets, transmitter A sends anacknowledgement request packet 410 to request that an acknowledgementpacket be sent back to transmitter A. The acknowledgement request packetmay be separate from the last data packet in the burst by the reducedinterframe spacing.

FIG. 5 is a diagram showing the transmission of the data packets and theacknowledgement request packet from transmitter A to receiver B and thetransmission of the acknowledgement packet from receiver B totransmitter A, as discussed with respect to FIG. 4. In accordance withthe present embodiment of the invention, transmitter A is capable ofsending data packets 402, 406, 408, and 410, as well as acknowledgementrequest packet 412 in quick succession, separated by the reducedinterframe spacing, which is less than the SIFS that may otherwise beutilized by transmitter A and receiver B. Receiver B is capable ofreceiving data packets 402, 406, 408, and 410, as well asacknowledgement request packet 412, spaced in this manner. Furthermore,receiver B is capable of receiving these packets and responding bygenerating and sending an acknowledgement packet 412 within a specifiedtime limit. This presents a significant challenge to receiver B, whichtypically must receive the data packets and acknowledgement requestpacket in receive mode, determine the outcome of the attempt to properlyreceive each of the incoming packets, generate an appropriateacknowledgement packet associated with such outcome, and convert totransmit mode to send out the acknowledgement packet. Receiver B mustcomplete all these steps within a specified time limit. The innovativeadoption of a reduced interframe spacing in accordance with the presentembodiment of the invention increases data throughput by compacting datapackets closer together than is allowed by existing MAC protocols, whichrequire a minimum separation of SIFS. However, use of the reducedinterframe spacing means that receiver B has even less time to performall of its necessary tasks and send out the appropriate acknowledgementpacket within the specified time limit. As described in further detailbelow, the present embodiment of the invention nevertheless adopts theuse of a reduced interframe spacing and illustrates techniques forovercoming such timing and processing challenges.

FIG. 6 demonstrates three different scenarios for receiving the datapackets and acknowledgement request packet shown in FIG. 4 andgenerating appropriate acknowledgement packet information, in accordancewith one embodiment of the present invention. Here, the transmission ofthe data packets, acknowledgement request packet, and acknowledgementpacket are all shown on a common line. However, it should be understoodthat the data packets and acknowledgement request packet are sent fromtransmitter A, and the acknowledgement packet is sent from receiver B,as previously discussed. As shown in the figure, for each of the threedifferent illustrative scenarios (i), (ii), and (iii), a check mark(“✓”) indicates successful reception of the respective data packet, andan x mark (“x”) indicates unsuccessful reception of the respective datapacket. A “successful” reception may be defined in different ways, asunderstood by one of ordinary skill in the relevant art. For example, ifa particular packet is received and a cyclic redundancy check (CRC)performed does not indicate any error, the packet may be considered tohave been received successfully. Of course, other definitions may beemployed.

For scenario (i), it is shown that all data packets 402, 404, 406, and408 have been received successfully. Here, each of the data packetscontains a distinct sequence number that distinguishes it from otherdata packets in this burst of data packets. For purposes ofillustrations, data packets 402, 404, 406, and 408 are shown to havesequence numbers 4, 5, 6, and 7, respectively. Continuing with scenario(i), the acknowledgement request packet 410 identifies the sequencenumber “4” as the leading data packet in the burst of data packets sent.In response to receiving all of the data packets 402, 404, 406, and 408successfully, the receiver sends an acknowledgement packet 412 thatidentifies the sequence numbers “4” and “7” to indicate the beginningand the end of a contiguous block of successfully received data packetsthat begins with the leading data packet.

For scenario (ii), FIG. 6 shows that data packets 402, 404, and 408 aresuccessfully received. However, data packet 406 is not successfullyreceived. Here, the acknowledgement packet 412 identifies the sequencenumbers “4” and “5,” which correspond to data packets 402 and 404,respectively. While data packet 408 is also shown to be receivedsuccessfully, the acknowledgement packet 412 only identifies thebeginning and end packets of a continuous block of successfully receiveddata packets beginning with the leading data packet. For this scenario,this block includes only data packets 402 and 404. Thus, theacknowledgement packet identifies corresponding sequence numbers “4” and“5.”

For scenario (iii), the figure shows that data packet 402 and 406 arenot received successfully, while data packets 404 and 408 are receivedsuccessfully. Here, there is no contiguous block of successfullyreceived data packets that begins with the leading data packet 402. Thisis because the leading data packet 402 is not successfully received. Inthis case, the acknowledgement packet indicates the leading sequencenumber as “4” and the ending sequence number as “3” (leading sequencenumber—1), to indicate that there is no contiguous block of successfullyreceived data packets beginning with the leading data packet.

The streamlined burst acknowledgement information illustrated in FIG. 6lessens the burden on a receiver responsible for generating and sendingan acknowledgement packet in response to a burst of data packets. Unlikepreviously implemented acknowledgement packets, the acknowledgementpacket shown in FIG. 6 needs not keep track of the successful orunsuccessful reception of every data packet sent in succession from thetransmitter, such as by inclusion of a bit map containing bits thatprovide a one-to-one correspondence to all such data packets. Inaccordance with the present embodiment of the invention, anacknowledgement packet may simply identify the beginning and end of acontiguous block of successfully received packets, thereby reducing theamount of processing the receiver must perform within a specified timelimit.

FIG. 7 is a flowchart outlining illustrative steps performed at areceiver for processing received data packets and processing receivedacknowledgement request packets, in accordance with one embodiment ofthe present invention. Specifically, a sub-flowchart 700 provides stepsfor processing a received data packet, while a separate sub-flowchart750 provides steps for processing a received acknowledgement requestpacket. According to the present embodiment of the invention, thereceiver maintains a data structure, referred to here as a “burst ackstate,” containing the following fields:

-   -   STA id    -   TC id    -   LSN (left sequence number)    -   RSN (right sequence number)

The burst ack state is initially reset. In the present embodiment of theinvention, this involves setting each field in the burst ack state to avalue of “0.” The STA id identifies the node from which the currentreceived packet originates. The traffic category (TC) id identifies thetraffic category of the current received data packet, when multipletraffic categories are applicable, such as when the present embodimentof the invention is used in a hybrid coordination function (HCF) system.Thus, the TC id may not be used when multiple traffic categories are notapplicable. The LSN, or left sequence number, identifies the sequencenumber of the leading packet in a continuous block of successfullyreceived data packets. In the present embodiment, the sequence number ofthe leading packet is identified in the acknowledgement request packet.The RSN, or right sequence number, identifies the sequence number of theending packet in the continuous block of successfully received datapackets.

In the present embodiment of the invention, one burst ack state ismaintained in real time at each receiver, even if the there are multipleflows of data that are handled by the receiver at a particular time. Theburst ack state is maintained in real time in the sense that theinformation in the burst ack state is closely updated in hardware tokeep up with the burst currently being received. There may be other datastructures maintained by the receiver that are not updated as closely,containing similar information and relating to other flows of data. Inanother embodiment of the invention, multiple burst ack states may bemaintained in real time at a receiver to correspond to multiple activeflows of data handled by the receiver.

Futhermore, in accordance with one embodiment of the present invention,a transmitter may use different values of reduced interframe spacing totransmit packets to different receivers. The various receivers may havedifferent capabilities such that one receiver may be capable ofreceiving packets separated by a particular value of reduced interframespacing, while another receiver is capable of receiving packetsseparated by another value of reduced interframe spacing. Thus, thetransmitter may be configured to automatically adjust the value of thereduced interframe spacing used in transmitting packets, depending onwhich receiver is to receive the transmitted packets. For example, thetransmitter may perform a look-up based on the identity of the receiver,in order to apply the appropriate reduced interframe spacing value.

In sub-flowchart 700, a data packet is received at step 702. At step704, the STA id and the TC id of the received data packet are examinedto see if they match those in the burst ack state. If not, at step 706,the STA id and TC id in the burst ack state are set to the those of thereceived data packet. Following step 706, in step 708, the LSN and RSNin the burst ack state are set to the sequence number of the receiveddata packet. Following step 708, in step 710, subsequent processing maybe performed. If at step 704, the STA id and the TC id of the of thereceived data packet match those of the burst ack state, at step 712,the sequence number of the received data packet is examined. If thesequence number of the received data packet is equal to (RSN+1), theprocess moves to step 714, where the RSN is set to that sequence number.Else, the process moves to step 710, where subsequent processing may beperformed.

In sub-flowchart 750, a burst acknowledgement request packet is receivedat step 752. Next, at step 754, a determination is made whether (1) theSTA id and the TC id of the received burst acknowledgement requestpacket match those in the burst ack state and (2) the sequence numberidentified in the received burst acknowledgement request packet equalsLSN. If both (1) and (2) are true, then at a step 756, a burstacknowledgement packet is sent identifying the current value of RSN. Inan alternative embodiment, the burst acknowledgement packet mayidentify, in addition, the sequence number identified in the receivedburst acknowledgement request packet, in a manner similar to that shownin FIG. 6. Following step 756, in step 758, the burst ack state isreset. Following step 758, at step 760, subsequent processing may beperformed. If at step 754, it is found that (1) and (2) are not bothtrue, then at a step 762, a burst acknowledgement packet is sentidentifying a number equal to the sequence number (identified in thereceived burst acknowledgement request packet) minus one. Again in analternative embodiment, the burst acknowledgement packet mayadditionally identify the sequence number identified in the receivedburst acknowledgement request packet, in a manner similar to that shownin FIG. 6.

FIG. 8 illustrates a queuing structure and the various queue states aspackets are transmitted in a burst acknowledgement mode according to oneembodiment of the invention. Here, the transmitter maintains a headpointer, an acknowledgement pointer (ack pointer), and a tail pointerpointing to appropriate locations within a queuing structure containingrepresentations of data packets sent by the transmitter. The headpointer points to the next packet in the queue which is due to betransmitted. The ack pointer points to the oldest unacknowledged packetin the queue. The tail pointer points to the last packet in the currentburst of packets to be transmitted. As shown, queue state 802 representsa queue state before transmission begins for a burst of 5 packetslabeled as P1 through P5. Queue state 804 represents the queue stateafter packets P1 and P2 have been transmitted, but not yet acknowledged.Queue state 806 represents the queue state after packets P1 and P2 havebeen successfully acknowledged. As data packets are sent by thetransmitter and acknowledged, the head pointer and acknowledgementpointer move along in the queuing structure to keep track of which datapackets sent by the transmitter have been properly acknowledged by theintended receiver.

FIG. 9 is a flowchart 900 outlining illustrative steps performed at atransmitter associated with sending an acknowledgement request packetfollowing a burst of data packets, in accordance with one embodiment ofthe invention. At step 902, a burst of data packets are sequentiallysent from the transmitter. In step 904, at the end of the burst, a burstacknowledgement request packet is sent from the transmitter. The burstacknowledgement request packet identifies the sequence number of thefirst packet in the burst of data packets sent at step 902. Next, atstep 906, it is determined whether a corresponding burst acknowledgementpacket is received from a receiver within a specified amount of time,for example, within a defined point coordination function interframespacing (PIFS). If not, at step 908, the head pointer is set to the ackpointer, and at step 910, subsequent processing may be performed. If so,at step 912, both the head pointer and the ack pointer are set to avalue equal to the RSN value found in the received burst acknowledgementpacket from the receiver, plus one. Next, in step 910, subsequentprocessing may be performed.

According to one embodiment of the invention, the transmitter andreceiver operate together in a number of different modes of operation.For example, there may be three modes of operation:

-   1. Burst ack with reduced interframe spacing-   2. No ack with reduced interframe spacing-   3. Burst ack with SIFS

In the first mode of operation, the transmitter may send a burst of datapackets separated by a reduced interframe spacing, and the receiver maysend a burst acknowledgement packet in response, as previouslydescribed. In a second mode of operation, the transmitter may send aburst of data packet separated by a reduced interframe spacing, and thereceiver may not send a burst acknowledgement packet in response. Thismode may be useful in media application, such as voice and video, inwhich lossy transmission is acceptable and re-transmission of data maynot be necessary. FIG. 10 illustrates an approach for sending a burst ofdata packets separated by a reduced interframe spacing from atransmitter A, without any acknowledgement packet from a receiver B thatreceives the burst of data packets. In a third mode of operation, thetransmitter may send a burst of data packets separated by SIFS, and thereceiver may send a burst acknowledgement packet in response, inaccordance with existing protocol standards.

In a preferred embodiment of the present invention, the reducedinterframe spacing may be dynamically adjustable between zero and SIFS.FIG. 11 illustrates an approach for sending a burst of data packetsseparated by a reduced interframe spacing that has been adjusted to zerofrom a transmitter A, followed by a single acknowledgement packet from areceiver B for providing acknowledgement information with regard to theattempt to receive data packets in the burst, in accordance with oneembodiment of the present invention. The dynamically adjustable reducedinterframe spacing may be utilized in a variety of ways. For example, aparticular reduced interframe spacing may be used in connection with thefirst mode of operation in which the transmitter sends a burst of datapackets separated by the reduced interframe spacing, and the receiversends a burst acknowledgement packet in response. However, the reducedinterframe spacing may dynamically change to a different value uponswitching to the second mode of operation in which the transmitter sendsa burst of data packets separated by the reduced interframe spacing andthe receiver does not send any burst acknowledgement packet in response.

While the present invention has been described in terms of specificembodiments, it should be apparent to those skilled in the art that thescope of the present invention is not limited to the described specificembodiments. The specification and drawings are, accordingly, to beregarded in an illustrative rather than a restrictive sense. It will,however, be evident that additions, subtractions, substitutions, andother modifications may be made without departing from the broaderspirit and scope of the invention as set forth in the claims.

1. A method for transmitting data packets in a wireless network over amulti-access channel comprising: sequentially sending a plurality ofmedium access control (MAC) data packets from a transmitter over themulti-access channel, using a physical layer protocol based on astandard physical layer protocol having a short interframe spacing(SIFS), wherein the plurality of MAC data packets includes at least afirst data packet and a second data packet separated by a reducedinterframe spacing that is less than SIFS; attempting to receive theplurality of MAC data packets at a receiver using the physical layerprotocol, including the first data packet and the second data packetseparated by the reduced interframe spacing; and sending from thereceiver a single acknowledgement packet associated with attempting toreceive the plurality of MAC data packets.
 2. The method of claim 1wherein the single acknowledgement packet contains packet receipt statusinformation for less than all of the plurality of the MAC data packets.3. The method of claim 2 wherein the single acknowledgement packetcontains a first sequence number and a second sequence number toidentify a portion of the plurality of MAC data packets as having beensuccessfully received.
 4. The method of claim 3 wherein the firstsequence number and the second sequence number identify a leading packetand an ending packet, respectively, of a continuous block ofsuccessfully received packets.
 5. The method of claim 1 wherein thereduced interframe spacing is adjustable within a range between zero andSIFS.
 6. The method of claim 5 wherein the reduced interframe spacing isautomatically adjustable depending on identity of the receiver.
 7. Themethod of claim 1 wherein the wireless network utilizes an 802.11-basedphysical layer protocol.
 8. The method of claim 1 wherein the method isassociated with at least a first and a second mode of operation, whereinthe first mode of operation involves said steps for sequentially sendingthe plurality of MAC data packets, attempting to receive the pluralityof MAC data packets, and sending the single acknowledgement packet, andwherein the second mode of operation involves the steps of: from thetransmitter, sequentially sending a second plurality of MAC data packetsover the multi-access channel, wherein the second plurality of MAC datapackets includes at least a first data packet and a second data packetseparated by a reduced interframe spacing that is less than SIFS; at thereceiver, attempting to receive the second plurality of MAC datapackets, including the first data packet and the second data packetseparated by the second reduced interframe spacing, without sending fromthe receiver an acknowledgement packet associated with the attempt toreceive the second plurality of data packets.
 9. The method of claim 8wherein the method is further associated with a third mode of operationinvolving the steps of: from the transmitter, sequentially sending athird plurality of MAC data packets over the multi-access channel,wherein the third plurality of MAC data packets includes at least afirst data packet and a second data packet separated by SIFS; at thereceiver, attempting to receive the third plurality of MAC data packets,including the first data packet and the second data packet separated bySIFS; and sending from the receiver a single acknowledgement packetassociated with the attempt to receive the third plurality of MAC datapackets.
 10. The method of claim 8 wherein the reduced interframespacing is dynamically adjustable based on which mode of operation isselected.
 11. A method for transmitting data packets in a wirelessnetwork over a multi-access channel comprising: from a transmittercapable of sending packets separated by short interframe spacing (SIFS),sequentially sending a plurality of medium access control (MAC) datapackets over the multi-access channel, wherein the plurality of MAC datapackets includes at least a first data packet and a second data packetseparated by a reduced interframe spacing that is less than SIFS; at areceiver capable of receiving packets separated by SIFS, attempting toreceive the plurality of MAC data packets, including the first datapacket and the second data packet separated by the reduced interframespacing, without sending from the receiver an acknowledgement packetassociated with the attempt to receive the plurality of data packets.12. An apparatus for transmitting data packets in a wireless networkover a multi-access channel comprising: a transmitter capable of sendingpackets separated by short interframe spacing (SIFS), the transmitterfurther capable of sequentially sending a plurality of medium accesscontrol (MAC) data packets over the multi-access channel, wherein theplurality of MAC data packets includes at least a first data packet anda second data packet separated by a reduced interframe spacing that isless than SIFS; and a receiver capable of receiving packets separated bySIFS, the receiver further capable of attempting to receive theplurality of MAC data packets, including the first data packet and thesecond data packet separated by the reduced interframe spacing, whereinthe receiver is further capable of sending a single acknowledgementpacket associated with the attempt to receive the plurality of MAC datapackets.
 13. The apparatus of claim 12 wherein the singleacknowledgement packet contains packet receipt status information forless than all of the plurality of the MAC data packets.
 14. Theapparatus of claim 13 wherein the single acknowledgement packet containsa first sequence number and a second sequence number to identify aportion of the plurality of MAC data packets as having been successfullyreceived.
 15. The apparatus of claim 14 wherein the first sequencenumber and the second sequence number identify a leading packet and anending packet, respectively, of a continuous block of successfullyreceived packets.
 16. The apparatus of claim 12 wherein the reducedinterframe spacing is adjustable within a range between zero and SIFS.17. The apparatus of claim 16 wherein the reduced interframe spacing isautomatically adjustable depending on identity of the receiver.
 18. Theapparatus of claim 12 wherein the wireless network utilizes an802.11-based physical layer protocol.
 19. The apparatus of claim 12wherein the apparatus is associated with at least a first and a secondmode of operation, wherein in the first mode of operation, thetransmitter is capable of sequentially sending the plurality of MAC datapackets, and the receiver is capable of attempting to receive theplurality of MAC data packets and sending the single acknowledgementpacket, wherein the second mode of operation, the transmitter is furthercapable of sequentially sending a second plurality of MAC data packetsover the multi-access channel, wherein the second plurality of MAC datapackets includes at least a first data packet and a second data packetseparated by a reduced interframe spacing that is less than SIFS, andwherein in the second mode of operation, the receiver is further capableof attempting to receive the second plurality of MAC data packets,including the first data packet and the second data packet separated bythe second reduced interframe spacing, without sending anacknowledgement packet associated with the attempt to receive the secondplurality of data packets.
 20. The apparatus of claim 19 wherein theapparatus is further associated with a third mode of operation, whereinin the third mode of operation, the transmitter is capable ofsequentially sending a third plurality of MAC data packets over themulti-access channel, wherein the third plurality of MAC data packetsincludes at least a first data packet and a second data packet separatedby SIFS, wherein in the third mode of operation, the receiver is capableof attempting to receive the third plurality of MAC data packets,including the first data packet and the second data packet separated bySIFS, and sending a single acknowledgement packet associated with theattempt to receive the third plurality of MAC data packets.
 21. Theapparatus of claim 19 wherein the reduced interframe spacing isdynamically adjustable based on which mode of operation is selected. 22.An apparatus for transmitting data packets in a wireless network over amulti-access channel comprising: a transmitter capable of sendingpackets separated by short interframe spacing (SIFS), the transmitterfurther capable of sequentially sending a plurality of medium accesscontrol (MAC) data packets over the multi-access channel, wherein theplurality of MAC data packets includes at least a first data packet anda second data packet separated by a reduced interframe spacing that isless than SIFS; and a receiver capable of receiving packets separated bySIFS, the receiver further capable of attempting to receive theplurality of MAC data packets, including the first data packet and thesecond data packet separated by the reduced interframe spacing, withoutsending an acknowledgement packet associated with the attempt to receivethe plurality of data packets.
 23. A system for transmitting datapackets in a wireless network over a multi-access channel comprising:means for sequentially sending a plurality of medium access control(MAC) data packets from a transmitter over the multi-access channel,using a physical layer protocol based on a standard physical layerprotocol having a short interframe spacing (SIFS), wherein the pluralityof MAC data packets includes at least a first data packet and a seconddata packet separated by a reduced interframe spacing that is less thanSIFS; means for attempting to receive the plurality of MAC data packetsat a receiver using the physical layer protocol, including the firstdata packet and the second data packet separated by the reducedinterframe spacing; and means for sending from the receiver a singleacknowledgement packet associated with attempting to receive theplurality of MAC data packets.